Josephson junctions enable ultra-precise measurements, define the standard unit of electrical voltage, and serve as core components in many quantum computers. Despite their widespread use, the quantum-scale processes inside superconductors are extremely difficult to observe directly.
To address this challenge, researchers at the RPTU University of Kaiserslautern-Landau carried out a quantum simulation of the Josephson effect. Instead of working with solid superconductors, they separated two Bose-Einstein condensates (BECs) using an exceptionally thin optical barrier. This barrier was created with a tightly focused laser beam and moved in a controlled, periodic way. Remarkably, the atomic system produced the same defining signatures seen in real Josephson junctions. These included Shapiro steps, which are voltage plateaus that appear at multiples of the driving frequency. Published in the journal Science, the study serves as a clear demonstration of how quantum simulation can reveal fundamental physics.
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